Centro de astrobiología asociado al NASA Astrobiology Institute

Martian slope streaks as plausible indicators of transient water activity

Slope streaks have been frequently observed in the equatorial, low thermal inertia and dusty regions of Mars. The reason behind their formation remains unclear with proposed hypotheses for both dry and wet mechanisms.

Here, we report an up-to-date distribution and morphometric investigation of Martian slope streaks. We find: (i) a remarkable coexistence of the slope streak distribution with the regions on Mars with high abundances of water-equivalent hydrogen, chlorine, and iron; (ii) favourable thermodynamic conditions for transient deliquescence and brine development in the slope streak regions; (iii) a significant concurrence of slope streak distribution with the regions of enhanced atmospheric water vapour concentration, thus suggestive of a present-day regolith-atmosphere water cycle; and (iv) terrain preferences and flow patterns supporting a wet mechanism for slope streaks.

These results suggest a strong local regolith-atmosphere water coupling in the slope streak regions that leads to the formation of these fluidised features.

Image: Difference between low-volume mass wasting and slope streaks in HiRISE images. (a) Scree falls and talus deposits. The blue dotted ellipse differentiates the smooth texture of these mass movements from the rough-textured bed rock (violet dotted ellipse). The yellow dotted ellipse shows th e hazy texture corresponding to the downslope dust and talus deposits. (b) Streaks and mass wasting in Zunil Crater. The smaller red and yellow arrows in the upper left panel (January 2007) show similar albedo streaks on steep and gentle slopes, respectively. The orange rectangle in the June 2016 image shows the disappearance of the steep slope streak (in red rectangle). The blue arrows show the active mass movement slopes above the slope streak. The green and blue rectangles highlight the appearance of a new streak (marked by yellow rectangle). The yellow and violet rectangles show the difference in topography of the slope streak and the low-volume mass wasting, respectively, on the same slope. HiRISE image credit: NASA/JPL/University of Arizona.